U.S. Government contracts awarded to companies with alleged ties to terror groups, some of those terror groups targeting american forces. Abc's chief investigative correspondent brian ross on the trial. Reporter: With americans still being attacked every week in afghanistan, the u.S. Government has worked hard to find out who has helped pay for the continued and deadly insurveillance jent strikes only to discover that among those connected to the terrorists were working for the u.S. Government. According to these two lists produced by the military and the congress department. U.S. Officials say the companies already have received about $150 million in u.S. Taxpayer money over the years. It's like the united states government subsidizing the taliban al qaeda network, those groups that are trying to shoot and kill our soldiers. Reporter: Among them a road construction company that the u.S. Says is partly owned by a leader of that brutal network, blamed for an attack on the u.S. Became that killed 16 people. The company denies ties to terrorists but documents obtained by abc news claimed the profits, approximately 1 to $2 million a month flowed to the network to finance his activities. I'm an old time prosecutor and my hair stood on end. Reporter: An abc news investigation found that despite pleas from commanders in the field along with congress and the inspector general, pentagon lawyers have refused to formally block those companies from receiving u.S. Contracts. The reason they have given us is that it's not fair to these contractors that the evidence that we presented -- and this is the evidence collected by the united states government is classified. Reporter: The pentagon cancelled a scheduled interview with us on the subject so we went to the military office that deals with the issue where a top official said it was a question of due process, with classified information that the contractors cannot see. There are certain regulations that have to be followed, due process regulations. Even with groups that are connected to terrorism? Well, that gets into documents I cannot discuss. In fact, I'm not allowed to talk to you unless I have to end to interview at this time. In a statement to abc news the army said it has extensive vetting procedures and most of the companies on the terror connected list were not award contracts. Most they say, diane, does not mean all. Brian ross investigating again tonight. Thank you, brian.

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